120 



goo 



S 80 



1 



S 60 



z 

 o 



2 



Z 



40- 



o 



8 201- 



pH VIU.IS1 or ur 



INIIUi 



"cOICUCTVtTT or % 



4_ IMTUl 



IMTVl 

 /l^f W SAP 



iwTUL K n exTciWM. sounoM 



MmU. 8r IN CITCKNM. laUTKM 



5 6 



WEAN pH OF CULTURE SOLUTION 



I/) 

 O 



X 



z 

 8 % 



6 ^ 



> 



o 

 o 



5 a." 



Textfigure 16. — An experiment with excised barley roots 

 showing accumulation of salt (potassium and bromide ions) 

 from buffered solutions at various pH values. At all pH values 

 ions were found in sap at higher concentrations than those of 

 the external solutions. Potassium could be accumulated when 

 pH of the latter was either less or greater than that of ex- 

 pressed saps. Similar conclusions were supported by experi- 

 ments in which root exudates were studied. (From Hoagland 

 and Broyer, 1940). 



